This invention relates generally to fluid pressure regulator valves, and more particularly to a shutoff valve for shutting off the flow of a fluid under certain conditions, such as when an system pressure exceeds a predetermined pressure or where a gross leak develops in the delivery system downstream from the valve resulting in a dramatic increase in flow.
This invention has particular (albeit not exclusive) application to regulating the flow of gas, such as gas used for fuel. Conventional gas regulators function to establish and maintain a substantially constant delivery pressure in a system as the source (e.g., cylinder) pressure changes in response to temperature and other conditions. Gas systems also typically incorporate a safety relief valve to vent pressurized gas in the event of a pressure control failure. At some predetermined pressure, the safety valve opens and gas is permitted to vent to the atmosphere at a rate proportional to the inlet pressure. Such pressure relief valves have at least two serious drawbacks. First, flammable and/or toxic gas is allowed to accummulate at or near the safety valve. This creates the risk of an explosion and fire. Moreover, the accummulated gas may pose a health hazard to persons in close proximity to the valve, especially in a confined space. Second, the relief valve may be incapable of venting gas at a rate sufficient to avoid substantial downstream pressure increases which may damage downstream components of the system.
There is also a need in the industry for an excess pressure shutoff valve which is responsive to a substantial drop in downstream pressure (due to a line rupture downstream from the valve, for example) to shut off the flow of fluid through the valve.